Consider adding software rendering water effects to OpenGL as a toggle

[Kiok17]

There is evidence to show Half-Life 1 maps were designed with the water of software rendering in mind, however software rendering forces low resolutions, and lower performance. Some people prefer the OpenGL water, as well as Opposing Force and Blue Shift maps being made with OpenGL in mind, so a toggle for this feature would also be appreciated.

[SamVanheer]

Graphical upgrades are out of scope for this project (see README.md for more information), but i'll leave this issue open if anybody wants to add this later when the project is open for community contributions.